What happens when a trendy New York department store meets a beautiful but untrendy, un-modern third-world nation?

When the store is Bloomingdale's and the country is India, the result is business. A lot of businee, in factr, about $7 1/2 to $8 million worth, plus a $1 million advertising, direct mail and promotion campaign to boost the sale of the merchandise.

Also a lot of travel - more than 100 trips to India by 75 Bloomingdale's staff members - and frustration and aggravation. One shipment of INdia goods now overdue at the White Flint store is afloat on a cruise ship in the Caribbean.

And while six full-scale stuffed horses meant for display (but priced for sale after the promotion) arrived tail-less, they were followed by a letter saying someone had forgotten to pack the tails. The tails arrived Friday by air in their own wooden crate.

The promition, called "India: The Ultimate Fantasy," which Marvin Traub, the store's president, calls "the largest selection of India consumer goods in the United States, and to our knowledge the largest ever outside of India." opens today at White Flint and Tyson's Corner and will continue in all 13 stores, here and in other cities, through May 20.

The project, a challenge to any store, even Bloomingdale's with its reputation for innovation and merchandising savvy, has turned traditional braclets into ashtrays, Bombay policemen's shirts (the prototype) bought off an officer's back on the streets of Bombay) into chic menswear, and silk saris into shower curtains with $100 price tags.

"We've taken a tradition and made it more Bloomingdale's" said Anne Bertsch, Bloomingdale's home-furnishings fashion coordinator, at a press conference at White Flint last week.

The kickoff this weekend was pure Bloomingdale's, too, with a black-tie gala Saturday night at the White Flint Store to benefit the women's committee of the Smithsonian Associates. Smithsonian Secretary S. Dillon Ripley was onhand to present a citation to retired Kentucky senator and former ambassador to India John Sherman Cooper. (Henry Kissinger has been snared for the New York opening. The Road to India

Bloomingdale's India connection started in 1966 with a scouting trip by store executives. But it was about a year ago, at the French ready-to-Traub took the plunge. He gave the wear shows in Paris, that Marvin go-ahead for a major sotre-wide assault on clotjing, home furnishings, arts and crafts from India.

Bloomingdale's was gambling. They were betting that the soft, loose look in clothing, then popular in the Paris and New York fashion centers, would hold up for the coming year. And they were hoping that India merchandise, which had flooded America in the past largely at cheap prices, could attract higher-paying customers, given Bloomingdale's deisgn and marketing moxie.

In July, Koko Hashim, then Bloomingdale's fashion director (now Neiman-Marcus vice president in charge of fashion merchandising) took off for India with two suticases. Crammed inside were 100 samples of front-running, advanced styles from all departments of the store. En route with a design team of seven, she stopped in Paris to pick up some more avantgrade styles.

The strategy was to have a mix of clothes worked up in India fabrics from designs chosen by Bloomingdale's - some made by American designers such as Willi Smith and DDDominick in India, and some original Indian designs.

"When I explained to the textile and manufacturing people in India that there was no price limit, it uncorked great enthusiasm and interest." says Hashim. "They had been tourtured for so long by people coming to India wanting something for nothing."

The task wasn't easy for the Indians, who seldom wear Western clothes and therefore had scant sense of the style, fit and colors Hashim and her team wanted.Many items were returned and returned again for revised samples.

But there were triumphs too. "At one time I remember crying," says Hashim. "I had given a manufacturer an almost impossible task, to engineer an oversized madras plaid in our colors into eight garments ... It shouldn't have been possible. And when it came through, I couldn't think of any way to improve it."

And there was another development.

When Japanese-born Kenzo Takada visited New York last fall, Bloomingdale's Leonard Rosenberg told him what the store was attempting. Kenzo reportedly said noting, but a major part of his collection for spring, shown several months later, included clothes clearly inspired by India.

Then "when I was riding in a taxi in Katamandu and saw every man going to work in a taxi in an oversized Western blazer, white tunic and skinny pants, just as Kenzo had showned it in Paris, it made me nuts it in the head," laughs Hashim. "How original is anythings?"

Kenzo's Indian-style designs made in Paris, plus thismenswear made by Bloomingdale's in India, are part of the collection. On to the TajMahal

Once the clothe samples were in the works, a troupe of 10, including four models and a hairstylist, left New York for India to shoot a 36-page color catalog in seven cities in 17 days. Packed into 58 pieces of luggage with the Indian merchandise were some distinctly American item - Topsiders, a Diane von Furstenberg dress, Danskin leotards and Bloomies panties - to be photographed there. (The undies ended up in black and white as an insert).

One irrestisitable setting, recalls senior vice president Gordon Clarke was the back of the Taj Mahal. But it wasn't easy. The first attempt to reach a photographically appropriate site at sunset almost founded when the boat carrying models and gear ran arround en route.

A reshooting was scheduled for dawn and cast and equipment were moved this time by two camels to the same site. But mist surrounded the Taj Mahal until snoon to be followed by too-bright sunlight, and the second picture wasn't unseable. (The picture taken in near darkness the night before is in the catalog.)

Air India helped out, furnishing guides and escorts and chipping in on ads where its name is mentioned. Whether other Indiaan companies contributed, no one will say. The only free ride, says the government-run airline, was for Indian craftsmen and artists flown here to appear at the stores this month. India on MY Mind

Marvin Traub's own attraction to India may be deeper than the clothes people wear (and can buy in his stores).

In an interview last May, when asked what he would most like to be "were he not the preisent of Bloomingdale's," Traub said, "Well, over the years we (my wife and I) have had personally a great interest in India and spent some time in that country. And I had thought that if I ever retired from retailing it might be a very adventerous assignment to take on the challenge of the job of being ambassador to India.

"But," he continued, "I've long since decided it may be presumptuous of me to think about it and it may be something that, when faced with the hard choice, I would have to think whether I was right or not. But I've been fascinated by the country and visited it and a number of our ambassadors there."

Whatever, at Saturday night's kick off party, Traub was still very much the Bloomingdale's retailer. Surrounded by the fruits of the year's labors, he took the first big order on Indian merchandise himself - a $750, full-size stuffed canvas elephant in black with ceremonial garb, bought by Washington insurance executive Huntington Block.